The objective of the research is to demonstrate the feasibility and utility of a new analytical instrument capable of single cell detection and genetic analysis. The principal component of this approach is a micro-array of giant magnetoresistive (GMR) sensors to measure selected binding reactions. The system is referred to as BARC, which stands for bead array counter. The basic process involves labeling a selected analyte with a magnetic bead which is then detected by means of the magnetoresistive effect. The experimental plan is designed to establish proof-of-concept by using a prototype instrument based on an 8x8 array. System attributes will be established with the detection and characterization of a selected strain of yeast. Specific aims are to 1) develop the magnetic labels and assays for yeast cell capture, 2) apply surface patterning techniques to prepare an array of PNA probes, 3) design a prototype unit capable of performing all processing steps, 4) design a disposable cartridge system with integrated microfluidics, and 5) test the overall performance of the final prototype probe.